Superconductive device comprising a refrigeration unit, equipped with a refrigeration head that is thermally coupled to a rotating superconductive winding

ABSTRACT

The invention relates to a superconductive device containing a rotor that can be rotated about an axis of rotation and that comprises a superconductive winding in a winding support. Said winding support has a central cavity, into which two fixed thermal tubes project axially. One of said tubes forms a cooling finger that is closed at the end and contains a second coolant with a higher condensation temperature. The other tube supplies a first cooling with a lower condensation temperature to the central cavity and evacuates said coolant from the cavity. To condense the coolants, the tubes lead to a refrigeration unit, situated outside the rotor and equipped with a refrigeration head and a condenser device.

CROSS REFERENCE TO RELATED APPLICATION

This application is the US National Stage of International ApplicationNo. PCT/DE03/01052, filed Mar. 31, 2003 and claims the benefit thereof.The International Application claims the benefits of German Patentapplication No. 10221635.5 DE filed May 15, 2002, both of theapplications are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to a superconductive device with a rotor which ismounted so that it can be rotated about an axis of rotation and whichdisplays at least one superconductive winding, the conductors of whichare arranged in a winding support, and with a refrigeration unit whichdisplays at least one refrigeration head that is thermally coupled tothe winding. A corresponding device is disclosed by U.S. Pat. No.5,482,919 A.

BACKGROUND OF THE INVENTION

In addition to the long familiar metallic superconductive materials suchas NbTi or Nb₃Sn, which have very low transition temperatures T_(c) andare therefore also referred to as low T_(c) superconductive materials orLTS materials, metal oxide superconductive materials with transitiontemperatures of more than 77 K have been known since 1987. The lattermaterials are also referred to as high T_(c) superconductive materialsor HTS materials, and in principle enable a cooling technology usingliquid nitrogen (LN₂).

The attempt is also being made to produce superconductive windings withconductors by using such HTS materials. It has been found, however, thatconductors known to date only possess a relatively low current carryingcapacity in magnetic fields with inductions in the tesla range. Thisfrequently imposes the necessity that the conductors of such windings,in spite of the intrinsically high transition temperatures of thematerials used, must nevertheless be kept at a temperature level whichlies below 77 K, for example between 10 and 50 K, in order thus to beable to carry significant currents in the presence of field strengths ofa few tesla. Such a temperature level lies substantially higher than 4.2K, the boiling temperature of liquid helium (LHe), with which knownmetallic superconductive materials such as Nb₃Sn or NbTi are cooled.

Refrigeration units in the form of cryocoolers with a closed Hecompressed gas circuit are therefore preferably used in the saidtemperature range for cooling windings with HTS conductors. Inparticular, such cryocoolers are of the Gifford-McMahon or Stirling typeor are realized as so-called pulse tube coolers. Such refrigerationunits additionally have the advantage that the refrigeration power isavailable almost at the touch of a button and the user is spared thehandling of low-temperature liquids. Where such refrigeration units areused, a superconductive device such as a solenoid coil or a transformerwinding is only cooled indirectly by means of thermal conduction to arefrigeration head of a refrigerator (cf. e.g. “Proc. 16th Int. Cryog.Engng. Conf. (ICEC 16)”, Kitakyushu, JP, 20-24.05.1996, ElsevierScience, 1997, pages 1109 to 1129).

A corresponding cooling technique is also provided for a superconductiverotor of an electrical machine which can be taken from U.S. Pat. No.5,482,919 A. The rotor contains a rotating winding of HTS conductorswhich can be kept at a desired operating temperature between 30 and 40 Kby means of a refrigeration unit designed as a Stirling orGifford-McMahon or pulse tube cooler. For this purpose, therefrigeration unit contains, in a special embodiment, a co-rotatingrefrigeration head which is not described further in the specification,the colder side of which is thermally coupled to the winding indirectlyby way of thermally conducting elements. Furthermore, the refrigerationunit of the known machine comprises a compressor unit situated outsideits rotor which supplies the required working gas to the refrigerationhead by way of a rotating coupling, which is not described in detail ofa corresponding transfer unit. Additionally, by way of two slip rings,the coupling also supplies a valve drive mechanism of the refrigerationunit, which is integrated into the refrigeration head, with thenecessary electrical energy. This concept requires that at least two gasconnections must be routed coaxially and at least two electrical sliprings provided in the transfer unit. Additionally, the accessibility ofthe co-rotating parts of the refrigeration unit and in particular of thevalve drive mechanism in the rotor of the machine is hampered since therotor housing must be opened in the case of maintenance being required.Furthermore, the function of a conventional valve drive mechanism is notassured in the case of rapid rotation such as is present in the case ofsynchronous motors or generators.

SUMMARY OF THE INVENTION

The object of the present invention is to configure the device with thefeatures stated in the introduction, proceeding from this state of theart, in such a way that it can ensure reliable and cost-effectiveoperation of the refrigeration unit both in the cooling phase and alsoin the stationary state and in the case of rotation of the rotor in atemperature range below 77 K and with a reduced equipment cost bycomparison.

This object is achieved according to the invention with the measuresspecified in the claims. Accordingly, the superconductive devicecomprises a rotor which is mounted so that it can be rotated about anaxis of rotation and which displays at least one superconductivewinding, the conductors of which are arranged in a winding support, andalso a refrigeration unit which displays at least one refrigeration headthat is thermally coupled to the winding. In this respect, thesuperconductive device should display the following features,specifically:

-   -   that the winding support is equipped with a central cavity        extending in the direction of the axis, which is connected to a        lateral cavity leading laterally out of the winding support        area,    -   that the refrigeration head is situated in a fixed manner        outside the rotor and is thermally connected by means of a cold        surface to a condenser device for the purposes of condensing a        first and at least one further coolant in separate condenser        chambers, where the coolants differ in terms of their        condensation temperatures,    -   that a first fixed thermal tube for the first coolant and at        least one further fixed thermal tube for at least one further        coolant lead from the condenser device into the co-rotating        lateral cavity and where relevant into the area of the central        cavity,    -   that the first, open-ended thermal tube, the lateral cavity and        the central cavity are filled with the first coolant, where, in        an operating phase of the device, by exploiting a thermosyphon        effect, condensed coolant passes into the central cavity and        also coolant warmed and where relevant in the process of        evaporating there passes back via the first thermal tube again        to its condenser chamber,        and also    -   that at least one further thermal tube is realized as a cooling        finger that is closed at the end in the central cavity with a        filling of at least one further coolant, where, in a cooling        phase, by exploiting a thermosyphon effect, coolant condensed in        the condenser chamber of the tube is warmed by evaporation in        the area of the central cavity and coolant evaporated in this        way passes back to the condenser chamber.

In the configuration of the superconductive device according to theinvention, the entire refrigeration unit together with any of its movingparts is consequently arranged outside the rotor and therefore easilyaccessible at all times. The provision of the refrigeration power or thethermal transfer is effected from a fixed refrigeration head into therotor by way of the thermal tubes which assure the transport of therespective coolant without mechanically actuated parts. In this respect,the first coolant provided for continuous operation or the operatingphase is condensed by the release of heat at a condenser device, whichis connected to the refrigeration head in a highly thermally conductingmanner, in a circular process. The liquid condensate subsequently runsthrough the first thermal tube provided for this purpose into thelateral cavity of the rotor and from there into its central cavity ordirect into said cavity. The transport of the condensate through thefirst thermal tube takes place under the influence of gravity on thebasis of a so-called thermosyphon effect and where relevant by means ofthe capillary force of the internal wall of the thermal tube. For thispurpose, this tube acts as a “wick” in the intrinsically known manner.This function can be further optimized by means of appropriateconfiguration or lining of the internal wall. At the end of the firstthermal tube, the condensate drips or runs into the cavity provided. Thecondensate situated in the area of the winding is at least partiallyevaporated there by the absorption of heat. The first coolant then flowsthrough the interior of the first thermal tube back into the condenserdevice. In this respect, the return flow is driven by a slightoverpressure in the central cavity, acting as the evaporation part,relative to the parts of the condenser device acting as a condenser.This partial vacuum generated by the creation of gas in the evaporatorand the liquefaction in the condenser results in the desired return flowof coolant. Corresponding coolant flows are intrinsically known fromso-called “heat pipes”.

At least one further thermal tube, which is filled with a gas whichalready condenses at higher temperatures such as nitrogen, argon or ahydrocarbon, for example, as a further coolant, represents a coolingfinger which projects into the central cavity and is closed at the endthere. The thermal transfer during a cooling phase is effected up tothis tube end by exploiting a thermosyphon effect by means ofcondensation and evaporation of the further coolant. From this tube endin the area of the central cavity, thermal transfer to the parts of therotor to be cooled is effected by means of convection. The temperaturedifference of a few Kelvin arising in this respect between the end ofthe cooling finger and the wall of the central cavity is entirelyacceptable for the purposes of precooling.

In the case of the superconductive device according to the invention,therefore, two different cooling methods are combined. A first method,which represents pure thermosyphon cooling, provides a working gas as afirst coolant for the purposes of cooling during the operating phase.Only in conjunction with this first method of convective cooling canfurther thermosyphons with other gases (i.e. with at least one furthercoolant), and therefore other working temperatures, be simultaneouslythermally coupled to the parts of the rotor to be cooled (=furthermethod). This enables effective and inexpensive precooling in thepresence of optimum exploitation of the refrigeration power of therefrigeration head.

Further advantages of the configuration of the superconductive deviceaccording to the invention can be seen in the fact, among others, thatno moving parts such as fans or pumps, for example, are required forrecirculating the coolant. Additionally, the refrigeration unit can beeasily adapted to the different requirements of a machine installation.In particular, thermal tubes several meters long can be provideddepending on the design, with the result that, for example, arefrigeration machine can be mounted in an accessible place tofacilitate its maintenance while the actual motor or generator isinstalled in a manner that is difficult to access. The thermal transferor the provision of the refrigeration power is therefore particularlysimple and cost-effective in the case of the configuration according tothe invention.

Advantageous configurations of the superconductive device according tothe invention arise from the dependent claims.

Thus, a plurality of further thermal tubes in the form of coolingfingers with fillings of further coolants, which differ in terms oftheir condensation temperatures, can naturally be provided. Multi-stagecooling is enabled in this way.

Furthermore, particularly simple sealing of the coolant chamber can beachieved as a result of the fact that the central cavity is closed bythe winding support on one side and the lateral cavity is sealed by asealing device with co-rotating parts on the side facing therefrigeration head. In this respect, at least one seal in the categoryferrofluid seal, labyrinth seal, diaphragm gland can preferably beconsidered for the sealing device.

In practise, all types of refrigeration machines which display arefrigeration head which can be set to a predetermined temperature levelcan be provided as the refrigeration unit. Cryocoolers, particularlywith a closed He compressed gas circuit, are preferably provided sincethey display a simple structure and are particularly suited to anindirect cooling technique as in the case of the superconductive deviceaccording to the invention. Corresponding coolers, also referred to asregenerative cryocoolers, display a regenerator or regenerative workcycle in line with the customary classification of cryocoolers (cf. e.g.the said volume of Proceedings, pages 33 to 44).

By way of particular advantage, the refrigeration head can be realizedas a multistage head. Effective precooling in particular is thenpossible with its second, by comparison warmer, stage.

It must additionally be seen as advantageous if the winding to be cooledand therefore its superconductive material can be kept at a temperaturebelow 77 K, and in the case of the use of HTS material preferablybetween 20 and 50 K, by means of the refrigeration head. In thistemperature range, which can be adhered to with relatively limitedcooling effort, known HTS materials in fact display a critical currentdensity that is sufficient for customary applications. The requiredrefrigeration power can be found without difficulty in the case of thesuperconductive device according to the invention. It lies in the rangefrom a few tens of Watts at 20 K to 30 K for a synchronous machine ofthe size class of around 1 up to a few tens of Megawatts of mechanicalpower, for example.

Moreover, it must be seen as advantageous if the lateral cavity widensin the direction of the central cavity. Then in fact, centrifugal forcecan also possibly be exploited as a supporting factor alongside gravityfor the purposes of transporting the first coolant.

Further advantageous embodiments of the superconductive device accordingto the invention arise from the dependent claims which are not addressedin the foregoing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, preferred exemplary embodiments of the superconductivedevice in accordance with the invention are explained in further detailon the basis of the drawing. In this respect, the diagrams show thefollowing, in a longitudinal section in schematic form in each case:

FIG. 1 an embodiment of the rotor of a superconductive device,

FIG. 2 a refrigeration unit for this rotor and also

FIG. 3 an extract from a further superconductive device in accordancewith the invention.

In the diagrams, corresponding parts are labeled with the same referencesymbols.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of superconductive devices according to the inventionhighlighted on the basis of the diagrams in the following can constitutea (synchronous) motor or a (synchronous) generator in particular in eachcase. The superconductive device comprises a rotating superconductivewinding, which in principle permits the use of metallic LTS material(low T_(c) superconductive material) or oxidic HTS material (high T_(c)superconductive material). MgB₂ can also be considered as asuperconductive material. For the following exemplary embodiments, letan HTS material such as the known (Bi,Pb)₂Sr₂Ca₂Cu₃O_(x), for example,be selected. The winding can consist of a coil or a system of coils in a2-pole, 4-pole or other multipole arrangement. The outline structure ofthe parts of such a superconductive device forming a synchronousmachine, for example, that are situated in the area of the rotor, can beseen in FIG. 1, which is based on known embodiments of such machines(cf. the said U.S. Pat. No. 5,482,919 A or WO 00/13296 A, for example).

The only partially shown device generally designated by 2 comprises afixed outer housing 3 at ambient temperature with a stator winding 4.Inside the outer housing and enclosed by the stator winding 4, a rotor 5is mounted in bearings 6 so that it can be rotated about an axis ofrotation A. The bearings 6 can constitute conventional mechanicalbearings or magnetic bearings. In this respect, the rotor displays asolid axial rotor shaft part 5 a mounted in the corresponding bearing onone side. Furthermore, it contains a vacuum vessel 7 in which a windingsupport 9 with an HTS winding 10 is supported on, for example, hollowcylindrical suspension elements 8 transmitting torque. Within thiswinding support, a cylindrical cavity extending in the direction of theaxis, which is referred to as the central cavity 12 in the following,exists concentrically to the axis of rotation A. In this respect, thewinding support is implemented in a vacuum-tight manner with referenceto this cavity. It closes said cavity on the side facing the rotor shaftpart 5 a. On the other side, the central cavity 12 is connected to anaxial lateral cavity 13 with a smaller diameter by comparison, i.e. ittransitions into said cavity. This lateral cavity leads outwards fromthe area of the winding support out of the area of the outer housing 3.A tube-shaped rotor shaft part mounted in one of the bearings 6 andenclosing this lateral cavity 13 is designated by 5 b.

The superconductive device 2 furthermore displays a refrigeration unit,which can be seen in detail in FIG. 2, for indirectly cooling itswinding 10 by way of thermally conducting elements. This refrigerationunit generally designated by 15 comprises at least one refrigerationhead 16. The refrigeration unit can constitute a cryocooler of theGifford-McMahon type in particular. A pulse tube cooler or splitStirling cooler is preferably chosen as a regenerative cryocooler. Inthis respect, the refrigeration head 16 and therefore all essentialfurther parts of the refrigeration unit should be situated outside therotor 5 and the outer housing 3. Accessories required for therefrigeration unit together with refrigeration head to be used such aswarm pressure equalization vessels, filling capillaries and overpressurevalves for safeguarding the system against overpressure in the case ofwarming up, for example, are not shown in the diagram but are generallyknown. The refrigeration head 16 arranged 0.5 to a few meters laterallyfrom the rotor 5, for example, projects into the vacuum V′ of a vacuumvessel 23 with a thermal transfer body, for example, and displays a coldor heat exchanging surface 17 at its cold end. At least twovacuum-insulated, fixed thermal tubes 19 and 20 are thermally coupled tothis cold surface. These thermal tubes widen to a larger heat exchangingcross section in the area bordering on the cold surface 17 in each caseand there form widened condenser chambers 19 a and 20 a. The condenserchambers can thus be seen together with the cold surface 17 as a coolantcondenser device or coolant condensation unit 18.

Of the thermal tubes 19 and 20, the tube 20 is referred to as a firstthermal tube in the following and the tube 19 as a further thermal tube.These thermal tubes project laterally in an axial area into the lateral,co-rotating cavity 13 of the rotor. A tube 24 is provided for thispurpose, being fixed and concentric with reference to the axis A, andreferred to as an insertion or mounting tube in the following, whichencloses the thermal tubes 19 and 20 at least into the area of thelateral cavity 13. This mounting tube can be introduced laterally intothe cavity 13. For the purposes of sealing this mounting tube 24radially with respect to the tube-shaped rotor shaft part 5 b delimitingthe lateral cavity 13, use is made of a sealing device 21 not shown indetail in the diagram which can be realized as a ferrofluid seal and/ora labyrinth seal and/or a diaphragm gland, for example. A vacuum V,which is connected to the vacuum V′ in the vacuum vessel 23, forexample, applies in the mounting tube.

By way of advantage, precooling of the parts of the rotor 5 to be cooledcan be effected with the aid of the further thermal tube 19. For thispurpose, this thermal tube projects as a cooling finger into the centralcavity 12 where the tube is closed at one end 19 b. In this respect, thetube 19 should be filled with a further coolant k₂ such as N₂, forexample, which displays a second condensation temperature T_(k2) whichin general lies above the operating temperature of the superconductivematerial used for the winding 10. In a cooling phase, this furthercoolant k₂ condenses in the condenser chamber 19 a of the condenserdevice 18 of the refrigeration unit 15. By exploiting a thermosyphoneffect, it is warmed in the area of the central cavity 12 and passesback to the condenser device 18 in the thermal tube 19.

By way of the first thermal tube 20 and the lateral cavity 13, thecentral cavity 12 is connected to the heat exchanging area of thecondenser device 18 in a manner that is sealed gas-tight to the outside.A first coolant enclosed in these chambers such as Ne, for example, iscondensed by the release of heat at the cold surface 17 of therefrigeration head 16 in the area of the condenser device 18 in acircular process. The condensate liquefied in this way, designated by k₁and indicated by means of a heavy line in the diagram, subsequentlyflows through the first thermal tube 20, initially through the area ofthe lateral cavity 13 and from there into the central cavity 12. In thisrespect, the transport of the condensate through the thermal tube takesplace by means of a thermosyphon effect under the influence of gravity.For this purpose, the thermal tube 20 can be slightly inclined (by a fewdegrees) with respect to the axis of rotation A by way of advantage, inorder thus to support the flowing of the liquid coolant k₁ out of theopen end 20 b of the tube 20. Where relevant, the coolant transport isalso supported by means of a capillary force effect of the internal wallof the thermal tube, which functions as a “wick”. The function of such awick can be further optimized by means of appropriate embodiment, suchas with the aid of longitudinal ribs or channels for the purposes ofenlarging the surface area or by means of lining of the internal wall ofthe tube. The outflow of the condensate k₁ into the cavity 12 at the end20 b of the first thermal tube 20 can be further reinforced by means ofa particular shaping of this end, for example as a drip rim. Similarly,the shaping can also be in such a form that the dripping is supported bymeans of a gas movement in the rotating internal chamber on the basis ofa wind of the gaseous part of the coolant in the case of rotation.

If the thermal tube 20 ends earlier in the area of the lateral cavity13, the transport of this coolant k₁ into the central cavity 12 canpossibly be further supported by exploiting gravity and/or centrifugalforce by the fact that the lateral cavity 13 is in the form of a tubewidening with reference to its diameter in the direction of the centralcavity 12.

The liquid first coolant or condensate k₁ is then evaporated in theinterior of the rotor. The evaporated coolant is designated by k₁. Thiscoolant k₁ evaporated by the absorption of heat then flows through theinterior of the first thermal tube 20 back into the condenser chamber 20a of the condenser device 18. In this respect, the return flow is drivenby a slight overpressure in the central cavity 12, acting as theevaporator, relative to the condenser device, which is caused by thecreation of gas in the evaporator and the liquefaction in the condenserdevice. Evaporated coolant k₁ also fills the space between thetube-shaped rotor shaft part 5 b and the mounting tube 24 up to thesealing device 21.

In the superconductive device according to the invention, therefore, thefirst thermal tube is statically coupled to a refrigeration machine.This provides a transfer of the coolant into the cryogenic area, wherethe transition between fixed and rotating parts is effected by means ofdripping liquid and the return path by means of flowing gas.

According to the invention, at least two different coolants k₂ and k₁with a different boiling or condensation temperature (T_(k)) should beprovided for the purposes of the cooling and the precooling during theoperating phase. In this respect, the coolant designated as the furthercoolant k₂ should display a second condensation temperature Tk₂ which ingeneral lies above the operating temperature provided for continuousoperation of the superconductive winding. Nitrogen (condensationtemperature 77.4 K at normal pressure, triple point at 65 K, criticalpoint at 125 K and 22 bar) or argon (condensation temperature 87.3 K atnormal pressure, triple point at 85 K, critical point at 145 K and 38bar), for example, can be considered for this further coolant k₂depending on the operating temperature. On the other hand, the firstcoolant k₁ should possess a lower condensation temperature (T_(k1)) bycomparison. This temperature can be chosen such that the operatingtemperature of the superconductive winding lies only slightly higher,for example up to 20 K, than this condensation temperature. Therefore,hydrogen (condensation temperature 20.4 K at normal pressure, triplepoint at 14 K, critical point at 30 K and 8 bar) or neon (condensationtemperature 27.1 K at normal pressure, triple point at 25 K, criticalpoint at 42 K and 20 bar) can preferably be used as the first coolantk₁. Corresponding examples of coolant pairs k₁/k₂ comprise neon (T_(k1)of 27.1 K)/argon (T_(k2) of 87.3 K) or the coolant pair neon/nitrogen(T_(k2) of N₂:77.4 K) or hydrogen (T_(k1) of 20.4 K)/nitrogen as thecoolant pair if an operating temperature is to be provided which liesbelow T_(k2) and amounts to around 25 K, for example. At this operatingtemperature, therefore, at least one further coolant k₂ remains frozenor where relevant also liquid in the thermal tube 19.

For a cooling operation during a cooling phase, use is made of thefurther thermal tube 19 which is also coupled statically to therefrigeration machine 15. This cooling operation is described in furtherdetail in the following.

Since at least two coolants with different condensation temperatures areprovided according to the invention, in the case of a gradual cooling ofthe refrigeration head, at least one further coolant k₂ with the highestcondensation temperature (here: T_(k2)) will initially condense and bedrawn to the parts of the rotor to be cooled for the purposes of thermaltransfer as in the case of the first coolant in a closed thermosyphoncircuit.

Following corresponding precooling of these parts down to approximatelythe triple point temperature of this further coolant, said coolant willthen freeze in the area of the condenser device, upon which said deviceis cooled down to the condensation temperature of the next (first)coolant. In this way, given a suitable choice of coolants, almostcontinuous cooling can be implemented in the presence of optimumexploitation of the refrigeration power of the refrigeration head.

Naturally, corresponding stage-by-stage precooling with a plurality of(further) thermal tubes in the form of cooling fingers, which areprovided with fillings of different (further) coolants, which differ interms of their condensation temperatures, is also possible.

It was assumed in the case of the superconductive device 2 explained inthe foregoing that at least one refrigeration unit 15 possesses asingle-stage refrigeration head 16. This means that only one stage isprovided or exploited for making the refrigeration power available. Itis self-evident, however, that refrigeration heads realized in amulti-stage manner whose stages lie at different temperature levels arealso equally well suited. Thus, for example, in the case of acorresponding two-stage refrigeration head, the second (warmer) stagecan be connected to the condenser chamber 19 a of the further (second)thermal tube 19 for the second coolant k₂, while the condenser chamber20 a of the first thermal tube 20 for the first coolant k₁ can bethermally coupled to the first stage held at a lower temperature bycomparison. Effective precooling is possible by this means.

Where relevant, a power supply or a radiation shield can also be cooledby means of the second (warmer) stage of such a two-stage refrigerationhead.

In the case of the superconductive device 2, its winding body 9 can beimplemented in a sufficiently thermally conducting manner; i.e. it thendisplays highly thermally conducting parts between its wall to thecentral cavity 12 and the winding 10. By this means, the winding isthermally coupled to the cold surface 17 of the refrigeration head 16 ofthe refrigeration unit 15 in a simple manner by way of the winding body9, the coolant k₁ and k₁′ and the condenser chamber 20 a of thecondenser device 18. For the purposes of improving the heat transfer,measures enlarging the heat exchanging surfaces with reference to thecoolant k₁, k₁′, for example ribbing in the peripheral direction on thewinding support wall of the central cavity 12, can be provided whererelevant.

Naturally, the parts/containers enclosing the coolants k₁ and k₂ must beprotected against the introduction of heat. A vacuum environment isexpediently provided for the purposes of their thermal insulation,therefore, where insulants such as super-insulation or insulating foam,for example, can be provided additionally in the corresponding vacuumchambers where relevant. In FIG. 1, the vacuum enclosed by the vacuumvessel 7 is designated by V. It additionally surrounds the mounting tube24 enclosing the lateral cavity 13 and extending up to the seal 21. Thevacuum enclosing the thermal tubes 19 and 20 and also the condenserchambers 19 a and 20 a of the condenser device 18 and at least the coldsurface 17 of the refrigeration head 16 is designated by V′. Moreover,underpressure can also be generated where relevant in the chamber 22surrounding the rotor 5 and enclosed by the outer housing 3.

FIG. 3 shows a special configuration of a superconductive device 2′ witha refrigeration unit 15 (not shown) in the area of the transition from alateral cavity 13′ into a central cavity 12. In this respect, thelateral cavity, by way of a divergence from the embodiment shown in FIG.2, is implemented so that it widens in conical fashion in the directionof the central cavity 12 in an area 13 a. The mounting tube 24, fromwhich two thermal tubes 20′ and 19 for a first coolant k₁ and a furthercoolant k₂ project, ends in this widening area. The tube 19 representinga further thermal tube ends, in line with FIG. 2, in the area of thecentral cavity 12. On the other hand, the tube to be seen as a firstthermal tube 20′ has its open end 20 b in the widening area 13 a. Thefirst coolant k₁ emerges from this open end in liquid form. Evaporatedfirst coolant k₁ is fed by way of this thermal tube 20′, in a mannercorresponding to FIG. 2, to a condenser device for recondensation.

In the case of the embodiment of a superconductive device 2 or 2′ withrotor 5 shown in the diagrams, a once-only filling with the coolants isprovided. Insofar as the refrigeration unit is switched off and the coldparts warm up, the pressure in the tube or cavity system will rise bymeans of evaporation of the coolant. In this respect, the final pressureis dependent on the enclosed volumes and the quantity of the respectivecoolant in the system. If neon at

-   -   around 1 bar and 27 K and minimum liquid quantity is used as the        first coolant, for example, it can be assumed that following        warming up to ambient temperature of around 300 K, the pressure        will lie at more than 12 bar. Since this pressure places a load        on the rotating seal 21, it can be advantageous where relevant        to provide an external warm buffer volume. Insofar as this        volume amounts to n-times the cold volume of the coolant k₁,        k₁′, the pressure rise in the warm state can be reduced to        1:(n+1)-times by this means.

1-15. (canceled)
 16. A superconductive electric generating device,comprising: a rotor adapted to rotate about an axis of rotation; asuperconductive winding having a plurality of conductors arranged in awinding support; a refrigeration unit having a refrigeration headfixedly arranged outside the rotor and thermally coupled to thesuperconductive winding; a central cavity operatively associated withthe winding support extending in the direction of the axis and isconnected to a lateral cavity leading laterally out of a winding supportarea; a cold surface thermally connected to the refrigeration head andto a condenser to condense a first and a second coolant in separatecondenser chambers, the first and second coolants having differingcondensation temperatures; a first fixed thermal tube adapted totransfer the first coolant and a second fixed thermal tube adapted totransfer the second coolant, the first and second tubes extending fromthe condenser into a rotating lateral cavity and into an area withinwhich the following occurs: the central cavity, the first fixed thermaltube, and the lateral cavity are filled with the first coolant by athermosyphon effect; the condensed first coolant passes into the centralcavity and also the first coolant is warmed and passes back to itscondenser chamber via the first thermal tube by the process ofevaporation; and a third thermal tube sized and configured as a coolingfinger that is closed at an end located toward the central cavity andfilled with the second coolant via the thermosyphon effect that iscondensed in the condenser chamber of the third tube and is warmed byevaporation near the central cavity and passes back to the condenserchamber.
 17. The device in accordance with claim 16, wherein a pluralityof thermal tubes in the form of cooling fingers filled with coolantshaving different condensation temperatures are provided.
 18. The devicein accordance with claim 16, wherein the central cavity is closed by thewinding support on one side and the lateral cavity is sealed by asealing device with co-rotating parts on the side facing therefrigeration head.
 19. The device in accordance with claim 18, whereinthe sealing device is selected from the group consisting of: aferrofluid seal, a labyrinth seal, or a diaphragm gland.
 20. The devicein accordance with claim 16, wherein the refrigeration unit comprisingthe refrigeration head further comprises a regenerative cryocooler. 21.The device in accordance with claim 20, wherein the cryocooler comprisesa pulse tube cooler, a split Stirling cooler, or a Gifford-McMahoncooler.
 22. The device in accordance with claim 16, wherein there is amultistage realization of the refrigeration head.
 23. The device inaccordance with claim 17, wherein the refrigeration head displays tworefrigeration stages and the second stage is thermally connected to apower supply or a radiation shield and the first stage is cooler thanthe second stage and is thermally connected to the condenser chambers ofthe thermal tubes.
 24. The device in accordance with claim 22, whereinthe refrigeration head displays two refrigeration stages and the secondstage is thermally connected to the condenser chamber of the furtherthermal tube and the first stage is cooler than the second stage and isthermally connected to the condenser chamber of the first thermal tube.25. The device in accordance with claim 16, wherein the superconductivewinding operates at a temperature below 77 K.
 26. The device inaccordance with claim 16, wherein the conductors of the winding containlow T_(c) superconductive material or high T_(c) superconductivematerial.
 27. The device in accordance with claim 16, wherein the firstthermal tube is sized and configured as a drip rim towards an open endand projects towards the lateral cavity or into the central cavity. 28.The device in accordance with claim 16, wherein the lateral cavitywidens in the direction of the central cavity.
 29. The device inaccordance with claim 16, wherein the cold parts of the rotor and thethermal tubes are vacuum-insulated.
 30. The device in accordance withclaim 16, wherein the coolants are neon paired with nitrogen, neonpaired with argon, or hydrogen paired with nitrogen.
 31. Asuperconducting device, comprising: a condenser; a first tube adapted totransfer a first coolant; a second tube adapted to transfer a secondcoolant, the first and second tubes extending from the condenser into alateral cavity located toward the end of the device; a central cavitylocated toward the center of the device; and a third tube configured asa cooling finger that is closed at an end located toward the centralcavity and filled with the second coolant via a-thermosyphon effect thatis condensed in a condenser chamber of the third tube and is warmed byevaporation near the central cavity and passes back to the condenserchamber.
 32. The device as claimed in claim 31, wherein the condensedfirst coolant passes into the central cavity and is warmed and passesback via the first thermal tube to its condenser chamber by the processof evaporation.
 33. The device as claimed in claim 31, wherein the firstand second thermal tube, and the lateral cavity are filled with thefirst coolant by a thermosyphon effect.